Cell disruption, or lysis, is the first step in the extraction of nuclear acid, protein and other subcellular components from biological cells used in many biochemical and molecular analysis assays such as polymerase chain reaction (PCR). Cell lysis can be accomplished by either physical or chemical approaches. Chemical approaches use enzymes or detergents to dissolve cell members or walls. Physical approaches include the use of high speed blenders, high pressure liquid homogenizers, a French press, bead beating, sonication, freeze/thaw and grinding with a mortar and pestle. Among these methods, high-shear mechanical lysis such as French press is often the method of choice especially for breaking bacterial and yeast cells, and when enzymatic and detergent approaches are not compatible with subsequent processing steps. However, traditional high-shear mechanical cell lysis equipment require extremely high operating pressure (up to 40,000 psi) and the heating due to high power dissipation often leads to the denaturation of desired biomolecules. Moreover, such bulky, expensive and complex equipment cannot be used in portable devices for point-of-care diagnostics, environmental monitoring and pathogen detection.
Jiang F. Zhong, et al., “A microfluidic processor for gene expression profiling of single human embryonic stem cells,” Lab Chip, 2008, 8, 68-74, is a paper that demonstrates that the observed gene expression for a single human embryonic stem cell (hESC) is different than the gene expression observed for a plurality of hESC taken from the same individual. The paper suggests that heterogeneity of the mammalian cell populations may be a factor related to the observed expression variations in single-cell analysis of mammalian cells. The paper indicates that “[w]hen gene expression studies are conducted at the single-cell level, we must recognize that no two cells are identical.” Some of the reasons why this should be so include the variability in such factors as differences in cell cycle, differentiation stages, and environmental stimulation for different cells in a particular cell population. For a particular cell population, there can be variation of gene expression at the single-cell level, which may be due to stochastic expression fluctuation, or due to heterogeneity of the cell populations. In the procedures described in this paper, cells were chemically lysed, and their DNA and RNA contents were studied in a microfluidic system.
Existing mechanical cell lysis equipment do not have single cell lysis resolution which is required for single cell biological studies that are increasingly used in stem cell, embryonic development and cancer research due to the intrinsic heterogeneity in such cell populations.
There is a need for systems and methods that provide the ability to lyse individual cells under carefully controlled conditions.